This invention relates generally to radiotelephones or user terminals and, in particular, to an accessory module for providing location information for use by a radiotelephone or user terminal.
The use of position information that is widely broadcast, for example, the Global Positioning System (GPS), for obtaining location data, i.e., a terrestrial position fix including latitude, longitude, and possibly elevation, is widespread and well known. Time may also be calculated from GPS data. It has been proposed that user terminals or wireless stations in modern wireless telecommunications systems include a capability to receive GPS information and to thereby calculate their position on the surface of the Earth.
It is known to include GPS functions in a battery power module for a cellular telephone. Reference in this regard can be had, by example, to U.S. Pat. No. 5,786,789, issued Jul. 28, 1998, entitled xe2x80x9cGPS and Cellphone Unit Having Add-On Modulesxe2x80x9d, by J. Janky. In Janky, the electrical interface between the add-on module and the cell phone is implemented by UARTS communicating over two, unidirectional, serial lines. The electrical interface also utilizes the cell phone transmitter and receiver for transmitting GPS data from the add-on module to the cell phone. This electrical interface is not optimum for user terminals that are not adapted to receive information in these ways. A user terminal that does not have the requisite UARTS or serial lines available, or that does not have the capability to recognize information conveyed between UARTS, will not be capable of such communication. Also, user terminals that are not adapted to receive GPS data through their transmitter and receiver may not be able to operate with the GPS module disclosed in Jansky.
An accessory module that uses the same battery as the user terminal will consume power, and will thus negatively impact the talk and standby time of the user terminal. It is important that such an accessory module consume as little power as possible while performing its intended function(s), as well as when it is not performing its intended function(s).
The GPS system transmits two microwave carrier signals, a 1575.42 MHz carrier and a 1227.60 MHz carrier. These signals as received are attenuated (approximately xe2x88x92130 db). The mechanical placement of the accessory module components in relationship to each other is thus important in order to minimize signal length and to receive and amplify these signals, without introducing noise or crosstalk. The mechanical placement of the accessory module components is also important in that the accessory module should easily attach to the user terminal, and should also attach without interfering with the use of the terminal or with other accessories that may be attached.
For user terminals equipped with a GPS accessory module, a problem arises when the user terminal is out of view of the GPS satellite constellation. A server may be provided on the wireless network to receive position data from the user terminal, and based on additional information available, provide additional data to the user terminal for position determination. Reference in this regard can be had, by example, to allowed commonly assigned U.S. patent application Ser. No.: 09/547,089, filed Apr. 12, 2000, entitled xe2x80x9cGPS Assistance Data Delivery Method and Systemxe2x80x9d, by K. Pihl and H. Pirila. The disclosure of this patent application is incorporated by reference herein in its entirety insofar as it does not conflict with the teachings of the present invention.
It is an object and advantage of this invention to provide an improved accessory module for a user terminal that utilizes information broadcast from the GPS system to determine the user terminal""s position on the earth.
It is a further object and advantage of this invention to provide an improved electrical interface between the GPS accessory module and the user terminal.
It is a further object and advantage of this invention to provide a power management capability in the accessory module to reduce power consumption.
It is a further object and advantage of this invention to provide a mechanical interface between the components of the GPS accessory module, and also between the GPS accessory module and the user terminal.
It is another object and advantage of this invention to improve the accuracy of a GPS determined location by supplying additional data to a GPS accessory module from a position reference server on the wireless network that is accessible by the accessory module through the user terminal.
The foregoing and other problems are overcome and the objects of the invention are realized by methods and apparatus in accordance with embodiments of this invention.
A GPS accessory module for a user terminal is disclosed which includes an antenna for receiving GPS signals, circuitry for calculating location data from the GPS signals, and a communication unit. The communication unit is bi-directionally coupled to the calculating circuitry and manages communication between the circuitry and the user terminal. The communication unit includes an in-band modem for converting the calculated location data to a signal having a range of frequencies suitable for digitizing by a voice coder of the user terminal.
An energy management unit for the GPS accessory module is disclosed for controlling the power consumption of the module circuitry in response to information received from the user terminal.
A position reference unit in communication with said accessory is disclosed. The position reference unit includes circuitry for exchanging data with the communication unit and a position assistance task for providing assistance data to the said communication server. The position assistance data is used by the calculation circuitry for improving the calculation of the location data. The communication unit is further disclosed as including circuitry for initiating communication between the communication unit and the position reference unit through a wireless transmission channel.
The in-band modem of the communications unit is further disclosed as including circuitry for conveying a signal to the voice coder of the user terminal by an audio input signal and for receiving and demodulating another signal from an audio output of a voice decoder of the user terminal.
The GPS accessory module is further disclosed as including a connector coupled to a battery. The connector includes a power bus to convey power to both the accessory module and the user terminal, a signal for identifying the accessory module to the user terminal, and a signal which operates in two modes: as an input to the accessory module to cause a power up condition; and as an output to indicate battery temperature.
The GPS accessory is also disclosed as including a system connector which includes at least one digital data bus to convey control signals between the terminal and the accessory, and an analog signal bus to convey location data to the user terminal from the calculation circuitry. Both the battery connector and the system connector take advantage of pre-existing electrical interfaces within the user terminal.